Chain saw

ABSTRACT

A chain saw has an engine provided with a unique cooling arrangement. The engine is partially enclosed in a main housing of the chain saw and has a blower on one side thereof which is effective to direct air around substantial portions of the engine cylinder for cooling purposes. In accordance with the invention, a baffle is mounted on the cylinder to direct air along the side of the cylinder opposite the blower. This side of the cylinder further is provided with channels to facilitate movement of the air therealong, in a direction transverse to cooling vanes of the cylinder.

Uited States Patent 41.67, 4l.63,4l.62, 4l.61,41.60,41.64, 41.69, 41.68, 41.8, 143/32 2.644.435 7/1953 Hoxie l23/41.61 FOREIGN PATENTS 651.976 11/1962 Canada 143/32 Primary Examiner-Mark M. Newman Assistant Examiner-Cort R. Flint Attorney-Allen D. Gutchess, Jr.

ABSTRACT: A chain saw has an engine provided with a unique cooling arrangement. The engine is partially enclosed in a main housing of the chain saw and has a blower on one side thereof which is effective to direct air around substantial portions of the engine cylinder for cooling purposes. In accordance with the invention, a baffle is mounted on the cylinder to direct air along the side of the cylinder opposite the blower. This side of the cylinder further is provided with channels to facilitate movement of the air therealong, in a direction transverse to cooling vanes of the cylinder.

ReferencesCited UNlTED STATES PATENTS 1,715,749 6/1929 Gabrielson l23/4L62 I ll 1 34 t j 6 5 J 1 l 44 r @W \E. i 1 50 I PATENTEUJUN new INVENTOR. A THUR MFULLER mm.

ATTYs.

CHAIN sxw This invention relates to a chain saw and particularly to a chain saw engine provided with cooling means.

In most chain saw designs, the engine is mounted with the crankshaft horizontally disposed and with the ignition or spark plug end of the engine cylinder extending rearwardly in the direction opposite to the saw chain. The engine is partially enclosed in a main housing of the chain saw except for one side of the cylinder which has an exhaust port and muffler mounted thereon. The chain saw engine preferably is provided with a blower mounted on an extension of the crankshaft which supplies air around a substantial part of the cylinder enclosed within the main housing. This provides adequate cooling in most instances. However, the exposed side of the cylinder adjacent the exhaust port is subjected to overheating particularly if the saw is operated for a period of time under a heavy load.

In accordance with the invention, it has been found that an air-directing device or baffle can be mounted on the cylinder preferably adjacent the ignition end so as to receive air flowing past the cylinder end under the influence of the blower and direct this air around the exposed side of the cylinder adjacent the exhaust port. Further, this side of the cylinder is provided with channels which facilitate passage of air from the ignition end of the cylinder along the side thereof toward the exhaust port. These channels are preferably as deep as the cooling fins and communicate with the spaces between the cooling fins from the ignition end of the cylinder to the exhaust port. By the time the cooling air reaches the exhaust port, it is substantially dissipated and moves upwardly around the muffler fixed to the engine cylinder at the exhaust port.

The cooling arrangement according to the invention provides more uniform cylinder cooling which maintains the roundness or concentricity of the cylinder more fully to reduce combustion blow-down, which also maintains the crankcase at lower temperatures. The cooling also results in increased engine performance in terms of volumetric efficiency and reduces the overall heat of the chain saw, thereby effecting substantial reduction in vapor lock in gas lines and carburetor.

It is, therefore, a principal object of the invention to provide a chain saw engine with improved cooling means.

Another object of the invention is to provide a chain saw with an engine which is more uniformly cooled and operates more efficiently.

Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawing, in which:

FIG. I is a rear view in perspective of a chain saw embodying the invention;

FIG. 2 is an enlarged fragmentary view in horizontal cross section taken along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged, exploded view in perspective of cooling means associated with the engine; and

FIG. 4 is a fragmentary view with parts broken away and with parts in cross section of the cooling means of FIG. 3.

Referring to the drawing and more particularly to FIG. 1, chain saw embodying the invention is indicated at and includes a main housing 12 which also constitutes the main frame of the chain saw. An engine I4 is supported by the housing 12 and is mostly enclosed therein except for the right-hand side to which muffler 16 (see FIG. 2) is affixed. A crankshaft 18 in a crankcase 20 extends from this side of the engine and is connected to a sprocket (not shown) which drives a saw chain 21 supported on a mounting blade 22.

The crankshaft 18 has an extension 24 on the opposite side of the chain saw connected to an impeller 26 in a blower housing 28. This housing directs air along a side 30 of a cylinder 32 toward an ignition end 34 of the cylinder containing a spark plug 36. The air is directed by a shroud 38 located adjacent the blower cross the ignition end 34 of the cylinder parallel to cooling fins 40 located at this end and also directs air across the top and bottom sides of the cylinder. Normally, this air would then be dissipated directly outwardly away from the cylinder. It has been found, however, that when the chain saw particularly is operated under heavy load conditions and particularly for a continuous period of time, that an exposed side 42 of the cylinder 32 adjacent the muffler 16 tends to operate at higher temperatures than other portions of the cylinder 32 past which air is directed by means of the impeller 26 and the shroud 38.

In accordance with the invention, it has been found that by employing an auxiliary baffle or air-directing device indicated at 44, the air supplied around the end 34 of the cylinder 32 can be directed around and along the exposed side 42 of the cylinder. In order to effectively distribute this air over the side 42 of the cylinder, two channels 46 and 48 are formed in the side 42. The channels 46 and 48 are of U-shaped cross section and are of a depth substantially equal to the depth of cooling fins 50, located on the exposed side 42 of the cylinder. These channels do not have continuous surfaces but are formed by elimination of portions of the cooling fins 50. Consequently, air flowing through the channels 46 and 48 can also flow through spaces between the cooling fins 50, thereby providing effective distribution over the exposed side 42 of the cylinder. The passages begin at the base of the end cooling fins 40 and extend to a point adjacent an exhaust port extension 52 on the side 42 of'the cylinder, which extension 52 has an exhaust port which communicates with the muffler 16. The muffler 16 is affixed to the cylinder side 42 by fasteners extending into openings 53 in the port extension 52 and in a mounting post 54.

The air-directing device 44, as shown in FIGS. 3 and 4, includes a generally L-shaped shroud housing 55 having a first side 56 which is parallel with the ignition end 34 of the cylinder 32 and has end flanges 58 extending over the outermost ones of the end cooling fins 40 and are suitably affixed to the outermost fins as by rivets or other suitable fasteners extending through openings 60. The shroud housing 55 further has a second side 62 extending parallel to the side 42 of the engine cylinder and terminates in a lip 64. A pair of spaced turning vanes 66 and 68 are affixed to the side 62 of the shroud housing by suitable rivets 70 or other fasteners and have ends lying adjacent the first side 56. The spacing of the vanes 66 and 68 is such as to receive the air flowing past the end 34 on each side of the spark plug 36. The spacing also enables a muffler fastener to extend through an opening 72 into the opening 53 in the post 54. The turning vanes 66 and 68 are of arcuate shape and are effective to direct air flowing between the end cooling fins 40 into the channels 46 and 48 and therealong toward the exhaust port extension 52. This air is fully distributed over the side 42 of the engine cylinder and flows along the spaces between the cooling fins 50. With this arrangement, any tendency for overheating at the exposed side of the cylinder is substantially completely eliminated thereby causing the engine cylinder to operate at more uniform temperature and effect the advantages heretofore enumerated.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art and it is to be understood that such modifications can be made without departing from the scope of the invention, the embodiment shown and described being primarily for purposes of illustration.

Iclairn:

l. A chain saw comprising an engine including a crankcase with a horizontal crankshaft extending from one side thereof with an extension of the shaft on the opposite side operatively connected to a blower, a finned cylinder extending from said crankcase substantially perpendicularly to said crankshaft, enclosure means around said blower and forming -a passage for directing air around an ignition end of said cylinder opposite said crankcase, a baffle located adjacent said end of said cylinder on a side opposite said blower to direct air from the passage around the end of the cylinder to the side opposite the blower, said opposite side of said cylinder having fins transverse to the path of air directed therealong by said baffle, and channel means formed in said opposite side of said cylinder from the ignition end of said cylinder substantially to an exhaust port thereof in a direction generally parallel to the direction of the air and transverse to said fins to facilitate flow of air from said end of the cylinder along said opposite side of said cylinder substantially to said exhaust port.

2. A chain saw according to claim 1 characterized by said baffle having a turning vane to facilitate directing the air from said end to said opposite side of said cylinder.

3. A chain saw comprising an engine including a crankcase with a horizontal crankshaft extending from one side thereof with an extension of the shaft on the opposite side operatively connected to a blower, a finned cylinder extending from said crankcase substantially perpendicularly to said crankshaft, enclosure means around said blower and forming a passage for directing air around an ignition end of said cylinder opposite said crankcase, a baffle located adjacent said end of said cylinder on a side opposite said blower to direct air from the passage around the end of the cylinder to the side opposite the blower, said opposite side of said cylinder having fins transverse to the path of air directed therealong by said baffle, and two spaced, parallel channels in said opposite side of said cylinder in a direction generally parallel to the direction of the air and transverse to said fins to facilitate flow of air from said end ofthe cylinder along said opposite side ofsaid cylinder.

4. A chain saw according to claim 3 wherein said channel means have a depth substantially equal to the depth of said cooling fins on said opposite side of said cylinder.

5. A chain saw according to claim 3 characterized by said baffle having a turning vane for each ofsaid channels.

6. A chain saw according to claim 3 characterized by said shroud having a turning vane for each of said channels.

7. A chain saw according to claim 3 characterized by said baffle having a leg extending from said cylinder end substantially to said exhaust port.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 81 717 Dated June 1 1971 lnventofls) Arthur M. Fullerton It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On page 1 insert: Assignee The Scott & Fetzer Company In column 1, line 61, before "chain" insert -a--;

line 65, before "muffler" insert --a; line 74 for "cross" substitute -across--.

Signed and sealed this 12th day of October, 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GO'ITSCHALK Attesting Officer Acting Commissioner of Patents FORM USCOMM-DC 60376-P69 U 5 GDVER'JMEHT PRINTING OFFICE Y. 0-365-13 

1. A chain saw comprising an engine including a crankcase with a horizontal crankshaft extending from one side thereof with an extension of the shaft on the opposite side operatively connected to a blower, a finned cylinder extending from said crankcase substantially perpendicularly to said crankshaft, enclosure means around said blower and forming a passage for directing air around an ignition end of said cylinder opposite said crankcase, a baffle located adjacent said end of said cylinder on a side opposite said blower to direct air from the passage around the end of the cylinder to the side opposite the blower, said opposite side of said cylinder having fins transverse to the path of air directed therealong by said baffle, and channel means formed in said opposite side of said cylinder from the ignition end of said cylinder substantially to an exhaust port thereof in a direction generally parallel to the direction of the air and transverse to said fins to facilitate flow of air from said end of the cylinder along said opposite side of said cylinder substantially to said exhaust port.
 2. A chain saw according to claim 1 characterized by said baffle having a turning vane to facilitate directing the air from said end to said opposite side of said cylinder.
 3. A chain saw comprising an engine including a crankcase with a horizontal crankshaft extending from one side thereof with an extension of the shaft on the opposite side operatively connected to a blower, a finned cylinder extending from said crankcase substantially perpendicularly to said crankshaft, enclosure means around said blower and forming a passage for directing air around an ignition end of said cylinder opposite said crankcase, a baffle located adjacent said end of said cylinder on a side opposite said blower to direct air from the passage around the end of the cylinder to the side opposite the blower, said opposite side of said cylinder having fins transverse to the path of air directed therealong by said baffle, and two spaced, parallel channels in said opposite side of said cylinder in a direction generally parallel to the direction of the air and transverse to said fins to facilitate flow of air from said end of the cylinder along said opposite side of said cylinder.
 4. A chain saw according to claim 3 wherein said channel means have a depth substantially equal to the depth of said cooling fins on said opposite side of said cylinder.
 5. A chain saw according to claim 3 characterized by said baffle having a turning vane for each of said channels.
 6. A chain saw according to claim 3 characterized by said shroud having a turning vane for each of said channels.
 7. A chain saw according to claim 3 characterized by said baffle having a leg extending from said cylinder end substantially to said exhaust port. 